Combining Phenylalanine and Leucine Levels Predicts 30-Day Mortality in Critically Ill Patients Better than Traditional Risk Factors with Multicenter Validation.

In critically ill patients, risk scores are used; however, they do not provide information for nutritional intervention. This study combined the levels of phenylalanine and leucine amino acids (PLA) to improve 30-day mortality prediction in intensive care unit (ICU) patients and to see whether PLA could help interpret the nutritional phases of critical illness. We recruited 676 patients with APACHE II scores ≥ 15 or intubated due to respiratory failure in ICUs, including 537 and 139 patients in the initiation and validation (multicenter) cohorts, respectively. In the initiation cohort, phenylalanine ≥ 88.5 µM (indicating metabolic disturbance) and leucine < 68.9 µM (indicating malnutrition) were associated with higher mortality rate. Based on different levels of phenylalanine and leucine, we developed PLA scores. In different models of multivariable analyses, PLA scores predicted 30-day mortality independent of traditional risk scores (p < 0.001). PLA scores were then classified into low, intermediate, high, and very-high risk categories with observed mortality rates of 9.0%, 23.8%, 45.6%, and 81.8%, respectively. These findings were validated in the multicenter cohort. PLA scores predicted 30-day mortality better than APACHE II and NUTRIC scores and provide a basis for future studies to determine whether PLA-guided nutritional intervention improves the outcomes of patients in ICUs.

Stress Hyperphenylalaninemia Is Associated With Mortality in Cardiac ICU: Clinical Factors, Genetic Variants, and Pteridines.

OBJECTIVES: Hyperphenylalaninemia predicts poor outcomes in patients with cardiovascular disease. However, the prognostic value and factors associated with stress hyperphenylalaninemia (SHP) were unknown in critical patients in the cardiac ICU. DESIGN: Prospective observational study. SETTING: Single-center, cardiac ICU in Taiwan. PATIENTS: Patients over 20 years old with Acute Physiology And Chronic Health Evaluation II scores greater than or equal to 15 and/or ventilatory support in the cardiac ICU. INTERVENTIONS: We measured plasma phenylalanine levels serially during patients' stays in the ICU to investigate their prognostic value for 90-day mortality. Gene array was performed to identify genetic polymorphisms associated with SHP (phenylalanine level ≥ 11.2 µmol/dL) and to develop a Genetic Risk Score (GRS). We analyzed the associations between SHP and clinical factors and genetic variants and identified the correlation between pteridines and genetic variants. MEASUREMENTS AND MAIN RESULTS: The study enrolled 497 patients. Increased phenylalanine concentration was independently associated with increased mortality risk. Patients with SHP had a higher mortality risk compared with those without SHP (log rank = 41.13; p < 0.001). SHP was associated with hepatic and renal dysfunction and with genetic polymorphisms on the pathway of tetrahydrobiopterin (BH4) synthesis (CBR1 and AKR1C3) and recycling (PCBD2). Higher GRSs were associated with lower BH4 bioavailability in response to stress ( p < 0.05). In patients without SHP at baseline, those with GRSs gretaer than or equal to 2 had a higher frequency of developing SHP during the ICU stay (31.5% vs 16.1%; p = 0.001) and a higher mortality risk ( p = 0.004) compared with those with GRSs less than 2. In patients with SHP at baseline, genetic variants did not provide additional prognostic value. CONCLUSIONS: SHP in patients admitted to the ICU was associated with a worse prognosis. In patients without SHP, genetic polymorphisms associated with SHP measured using a GRS of greater than or equal to 2 was associated with the subsequent SHP and higher mortality risk.

U-Shape Relationship between Plasma Leucine Level and Mortality in the Intensive Care Unit.

Patients in the intensive care unit (ICU) are at high risk of mortality which is not well predicted. Previous studies noted that leucine has prognostic value in a variety of diseases. This study investigated whether leucine concentration was a useful biomarker of metabolic and nutritional status and 6-month mortality in ICU. We recruited 454 subjects admitted to ICU (348 and 106 in the initiation and validation cohorts, respectively) with an acute physiology and chronic health evaluation (APACHE II) score ≥ 15. We measured plasma leucine concentrations, traditional biomarkers, and calculated APACHE II and sequential organ failure assessment (SOFA) scores. Leucine levels were weakly correlated with albumin, prealbumin, and transferrin levels (r = 0.30, 0.12, and 0.15, p = 0.001, 0.029, and 0.007, respectively). During follow-up, 116 (33.3%) patients died. Compared to patients with leucine levels between 109 and 174 µM, patients with leucine > 174 µM or <109 µM had a lower cumulative survival rate. Death was also associated with age, higher APACHE II and SOFA scores, C-reactive protein, and longer stays in the ICU, but with lower albumin, prealbumin, and transferrin. Patients with leucine levels > 174 µM had higher alanine aminotransferase levels, but no significant differences in other variables; patients with leucine levels < 109 µM had higher APACHE II and SOFA scores, higher incidence of using inotropic agents, longer ICU and hospital stays, but lower albumin and transferrin levels. Multivariable analysis demonstrated that leucine > 174 µM was an independent predictor of mortality, especially early mortality. However, among patients who stayed in ICU longer than two weeks, leucine < 109 µM was an independent predictor of mortality. In addition, leucine < 109 µM was associated with worse ventilator weaning profiles. These findings were similar in the validation cohort. Our study demonstrated a U-shape relationship between leucine levels and mortality rate in ICU.

Elevated plasma phenylalanine predicts mortality in critical patients with heart failure.

AIMS: Previous studies found a relationship between elevated phenylalanine levels and poor cardiovascular outcomes. Potential strategies are available to manipulate phenylalanine metabolism. This study investigated whether increased phenylalanine predicted mortality in critical patients with either acute heart failure (HF) or acute on chronic HF, and its correlation with inflammation and immune cytokines. METHODS AND RESULTS: This study recruited 152 subjects, including 115 patients with HF admitted for critical conditions and 37 normal controls. We measured left ventricular ejection fraction (LVEF), plasma concentrations of phenylalanine, C-reactive protein, albumin, pre-albumin, transferrin, and pro-inflammatory and immune cytokines. Acute Physiology and Chronic Health Evaluation (APACHE II), Sequential Organ Failure Assessment (SOFA), and maximal vasoactive-inotropic scores (VISmax ) were calculated. Patients were followed up until death or a maximum of 1 year. The primary endpoint was all-cause death. Of the 115 patients, 37 (32.2%) were admitted owing to acute HF, and 78 (67.8%) were admitted owing to acute on chronic HF; 64 (55.7%) had ST elevation/non-ST elevation myocardial infarction. An LVEF measured during the hospitalization of <40%, 40-50%, and ≥50% was noted in 51 (44.3%), 15 (13.1%), and 49 (42.6%) patients, respectively. During 1 year follow-up, 51 (44.3%) patients died. Death was associated with higher APACHE II, SOFA, and VISmax scores; higher levels of C-reactive protein and phenylalanine; higher incidence of atrial fibrillation and use of inotropic agents; lower cholesterol, albumin, pre-albumin, and transferrin levels; and significant changes in pro-inflammatory and immune cytokines. Phenylalanine levels demonstrated an area under the receiver operating characteristic curve of 0.80 for mortality, with an optimal cut-off value set at 112 µM. Phenylalanine ≥ 112 µM was associated with a higher mortality rate than was phenylalanine < 112 µM (80.5% vs. 24.3%, P < 0.001) [hazard ratio = 5.07 (2.83-9.05), P < 0.001]. The Kaplan-Meier curves revealed that phenylalanine ≥ 112 µM was associated with a lower accumulative survival rate (log rank = 36.9, P < 0.001). Higher phenylalanine levels were correlated with higher APACHE II and SOFA scores, higher C-reactive protein levels and incidence of using inotropic agents, and changes in cytokines suggestive of immunosuppression, but lower levels of pre-albumin and transferrin. Further multivariable analysis showed that phenylalanine ≥ 112 µM predicted death over 1 year independently of age, APACHE II and SOFA scores, atrial fibrillation, C-reactive protein, cholesterol, pre-albumin, transferrin, and interleukin-8 and interleukin-10. CONCLUSIONS: Elevated phenylalanine levels predicted mortality in critical patients, phenotypically predominantly presenting with HF, independently of traditional prognostic factors and cytokines associated with inflammation and immunity.